African American adults are disproportionately affected by HIV/AIDS. Although much is known about HIV/AIDS, there is still a lack of comprehensive knowledge about the influence of sexual partners and substance use in the spread of HIV among heterosexual African American men and women. Certain aspects of the sexual partnership may impact consumption of substances, which in turn may reduce protective sexual behavior. The majority of research on HIV risk in African Americans has been based on samples of injection drug users and men who have sex with men. While useful, this limited scope may obscure the nature and degree of risk in other groups, such as those in partnerships involving alcohol and recreational drug use as well as partnerships in which condoms may be seldom used. It is important to track these interactions and behaviors daily, therefore the study will employ innovative experience sampling methodology (ESM). Using a community-based, non-clinical sample of 200 self-identified heterosexual African American men and women, the goal of the proposed project is to increase the scientific understanding of the episodic dimensions of sexual partners and substance use as they increase the risk of HIV transmission among African Americans. The project will also engage Kalamazoo College undergraduate students in meritorious, empirical and community-based, behavioral HIV research. The project is guided by three specific aims: Aim 1: Identify the role of sexual partner characteristics on episodic HIV risk-taking. It is expected that certain partner-level characteristics (e.g., context f partnership initiation), as well as the intentionality of these partnerships (e.g., level of commitment) will impact episodic HIV risk-taking, defined as: 1) engaging in unprotected sexual activity and 2) not inquiring about or requesting partner HIV testing. Aim 2: Assess the moderating effects of episodic substance use on the association between sexual partner characteristics and episodic HIV risk-taking. It is expected that substance use (e.g., type and amount, partner consumption) on the day of the sexual activity will increase the likelihood that intimate partner variables will predict increased episodic HIV risk. Aim 3: Explicate the constructed meaning and relevance of partner-level constructs to sexual risk-taking. It is expected that responses to a semi-structured interview will allow for elaboration and probing of responses provided during the experience sampling methodology (ESM) reporting. The specific aims described in this AREA proposal have been designed to include undergraduate students on the research team. Students working on the project will assist in collecting data from participants using mixed methods, analyzing data, and writing of manuscripts detailing findings from this study. The results will inform the development of more competent and effective targeted HIV-prevention interventions, including enhancing our understanding of the barriers to condom use and HIV testing in this group of African Americans.